Method of coating insulated wire or the like



June 23, 1936. A, CANDY, JR 2,044,970

METHOD OF COATING INSULATED WIRE OR THE LIKE Filed Dec. 18, 1933 HI |ll L/ZZ .1 .Z EJ 24:2

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Patented June 23, 1936 METHOD OF C DATING INSULATED WIRE OR THE LIKE Albert T. Candy, Jr., Oak Park, 111.

Application December 18, 1933, Serial No. 702,868

3 Claims.

This invention relates to a method of coating insulated wire or the like and more particularly to the manufacture of a flame repellent insulated wire for electrical circuits.

Insulated wires of the class layer overlying pregnated with a flame repellant material, a pi mented layer over outside waxy film or coating.

like with ease.

It has previously been proposed (Hinsky Patent No. 1,890,291) to apply the pigmented layer to the insulated wire, after impregnation with a. flame repellent pitch, by passing the wire through a. bed of a powdered mixture of waxes and pig- According to the Hinsky process, the flame repellant pitch is in a slightly tacky or plastic state as it passes through the bed of the and the wax is thereby caused to adhere in powdered conditionto the pitch impregnated surface of the fabric jacket. A final coating of wax is then applied to cover pigmented wax coating and thereby retain the powder against displacement from merits.

powdered, pigmented wax the powdered,

the jacket of the conductor.

According to my invention,

jacket of the wire,

pitch through a under the action of the saturated fabric and an.

The purpose of the outer wax coating is to give the insulated wire a sufficient degree of smoothness and slip to permit the wire to be pulled through conduits and the after the flame repellant pitch has been applied to the fabric the wire is passed while still at a temperature above the softening point of the bed of a powdered mixture of pigments and a suitable binder that will soften the heated wire and coalesce to form a dense, coherent pigmented layer over the fabric jacket. This pigmented layer is rendered more compressed and the fusion of any adhering particles of pigmented material is comforming rollpleted by passing the wire between ers and heated dies.

A dense, continuous and firmly anchored layer of pigmented material is saturated fabric jacket of the insulated though this pigmented process,

thus formed over the wire. Al-

coating, according to my will be ordinarily sufliciently smooth to serve as the outer coating for the insulated wire,

a final waxy coating may,

if desired, be applied in accordance with the usual practice in the manufacture of this type of wire. Such a coating, however, is not final wax necessary to anchor the pigmented layer or to maintain it against displacement, since by my method of manufacture this has already been accomplished in the previous steps. Therefore, the final wax coating, if applied, need be only a thin surface film for providing the desired smoothness and slip.

It is thus an important object of my invention to provide a relatively simple and economical method for the manufacture of insulated wire i a continuous operation, wherein a dense, coherent layer of pigmented'material is caused to adhere 1() strongly to and become anchored in the saturated fabric jacket of the wire.

It is a further important object of this invention to provide a method of making coated insulated wire that obviates the difficulties attendant upon 15 the use of molten baths of pigmented wax for applying the pigment layer.

Other and further important objects of this invention will become apparent from the following description and appended claims.

This invention (in a preferred form) is illustrated in the drawing and hereinafter more fully described.

On the drawing:

Figure 1 is a diagrammatic view, partly in sec- 5 tion, illustrating the method of my invention.

Figure 2 is a top plan view of a perforated drum of a type suitable for use in the saturating tank. Figure 3 is a fragmentary view taken substantially along the line III- II of Fig. 1.

Figure 4 is a detail view taken substantially along the line IV-IV of Fig. 1.

Figure 5 is a fragmentary elevational view of the wire broken away to show the different laminations.

As shown on the drawing:

The reference numeral ll'l indicates a vat or receptacle for containing a bath ll of flame repellant material, which may be any of the various pitchy substances commonly used for satu- 40 rating the fabric jacket of insulated wire. A perforated drum I2 is mounted horizontally within the vat In for rotation in the bath I l. A strand of wire I3 is adapted to be wrapped around the drum I2 for the requisite number of turns necessary to give the desired length of immersion time, which has been found to be about 25 seconds.

Means are provided for initially threading the wire about the druml2 and these means may suitably comprise a sprocket l4 secured on the drum shaft l5 and connected by means of a. sprocket chain IE to a second sprocket wheel I! on a stub shaft l8. A crank I9 is clutch connected to the shaft l8 for rotating the drum I! through the sprocket wheels I4 and I1 and the chain I6. Apertures 20 are provided at spaced intervals around the peripheral flange 2| at one end of the drum l2 to permit an end 22 of the wire l3 to be temporarily inserted through one of the apertures while the drum is being rotated by hand. In this way the desired number of turns of wire about the drum [2 may be made and then the end 22 removed from its aperture and started through the rest of the equipment.

The receptacle I is provided with suitable means for heating'the saturant in the bath I I to the temperature desired. Since, according to my method, the saturant is heated to a comparatively high temperature, say between 350 and 400 F., it is advantageous to use an electrical heating unit, as is illustrated at 23. By this means the bath ll of saturant is maintained at a temperature considerably above its melting point so as to reduce its viscosity and enable it to impregnate the fabric jacket of the wire more thoroughly. As the wire l3 leaves the rotating perforated drum l2, it passes through any suitable type of wiping device 24. The device 24 may be either a fabric wiper or die, or a metal die, or may be simply a strand of rope or fabric twisted around the wire I 3. excess of the saturant flows back into the bat I l.

The wire l3 ne t passes into a bed 25 composed of a mixture of dry, powdered pigment or coloring matter and a binder that softens under the action of heat. Any suitable form of receptacle 26 may be employedfor containing the bed 25. Since the wire traverses only a short air space between the saturating bath II and the, bed 25, it reaches the bed 25 at a sufficiently elevated temperature to cause the particles of the pigmented mixture to fuse and coalesce over the surface of the impregnated fabric jacket of the wire. Any loosely adhering pareter so as to reduce the ticles of the pigmented material may be removed as the wire passes out of the receptacle 26 through an aperture 21, die or the like, provided in one wall thereof. One or more sets of grooved rollers 28 is provided to compress the pigmented layer applied to the wire from the bath 25. If two or more sets of rollers 28 are employed, it is preferable to arrange succeeding sets of rollers in planes at an angle of 180', as illustrated by the sets of rollers 28 and 28a. Each set of rollers 28 comprises a pair of rollers 29 and 30 of identical construction and each provided witha groove 3| for encompassing approximately one half. of the periphery of the wire. Relieving grooves 32 and 33 may suitably be provided on each side of the wire receiving groove 3|, so as to take care of any excess of pigmented material adhering to the coated wire.

The wire l3 as it leaves the set of rollers 28 is preferably delivered in an inclined direction, as illustrated in Fig. 1, so as to require a minimum of supporting during its travel. A heated die 34, or a series of such dies, is provided for completing the fusion of the pigmented layer and for smoothing the pigment coating. If a series of dies 34 are used, they may be provided with graduated orifices of slightly diminishing diamdiameter of the pigment coated wire to the desired finished diameter. Each die 34 is heated to a temperature above the melting point of the binder used in the pigmented mixture, whereby a complete fusion of the binder is obtained and a certain proportion of the binder caused to flow to the surface of combustible nature may be added to the saturatof formulae for obtaining the coated wire and provide a smooth finish therefor.

Although it isnot necessary for many purposes, the coated insulated wire may be provided with a final film of wax or wax-like substance over 5 the pigmented layer. This film may be applied in avariety of ways, but as illustrated in Fig. 1, the wax may be applied from a plurality of atomizers 35. Alternatively, the strand of coated wire l3 may be passed through a bath of molten 1.) wax or through a bed of dry, powdered wax and then through one or more heated dies.

The coated insulated wire is. finally passed through a water bath 36 under a roller 31 positioned in a receptacle 38. The water bath is maintained at any suitable temperature for e1 fecting the congealing of the coatings on the wire. After leaving the bath 36, the wire passes over a roller 39 and is reeled up on a reel 40.

The finished wire, as illustrated in Fig. 5, comprises the wire proper 4|, a rubber sheet 42 surrounding the wire 4I, a fabric jacket 43 overlying the rubber sheet 42, and impregnated with a flame repellant substance, a pigmented layer 44 anchored to the impregnated fabric 43 and 5 an external film or coating 45 of wax or a waxlike substance. As previously explained, the external coating 45 may be omitted.

The composition of the bath I I may suitably be prepared by blending stearin pitch with various waxes, resins or gums in such proportions as to give a saturant having the desired melting point. Various vegetable and animal pitches may be used but stearin pitch has been found to be most suitable because of its flame repellant properties. Waxes such as paraffin wax, Montan wax, petrolatum, canauba wax and the like, and gums or resins, such as coumarone and indene resins may be admixed with the pitch. Also, if desired, various fillers or inorganic substances of a noning pitch. Preferably, the pitch bath I I is heated to a temperature of between 360 and 380 and the wire is given an immersion period of about 25 seconds. In general, the lower the temperature of the bath, the longer the immersion period should be.

In preparing the powdered mixture of pigment and binder, various pitches, waxes, or mixtures of the two may be employed. I 5

The composition of the pigmented mixture may be varied also depending upon the particular pigment that is employed although in general the mixture will contain over by weight of pigment. The following will illustrate suitable types different colors by the use of a pigmented mixture:

Red Gray Percent Percent by weight by weight Pitch 23 Pitch 20 Waxes 23 Waxes l 20 Pigment 54 Pigment 60 Owing to their greater covering power, since the saturant used for imparting flame repellant properties to the coated wire is usually a deep black.

The preparation of the powdered mixture of pigment and binder presents some difliculties in the grinding of the materials owing to the tendency of the waxes to pack and cake. These difflculties can largely be overcome by grinding the materials in a hammer mill type of mill at a relatively low temperature, namely a temperature below the softening point of the binder. The binder may either be ground separately and the pigment subsequently admixed therewith, or the mixture of binder and pigment may be ground together. Where some or all of the pigment content is added prior to grinding, the

grinding operation is rendered somewhat easier owing to the separating effect of the pigment on the particles of binder.

It will be apparent that the use of a powdered mixture of pigment and binder has distinct advantages over the use of molten baths of colored or pigmented wax, since it is possible by the use of a dry pulverized mixture to increase the pigment or color content very materially over that which is possible in the use of a molten bath. If a relatively large proportion of pigment is added to a molten wax bath, the bath becomes so viscous that difiiculties are encountered in drawing the insulated wire through the bath and obtaining an even coating. Furthermore, the increased pigment content made possible by the use of a dry powdered mixture of pigment and binder increases the flame repellant properties of the coated insulated wire.

As the wire passes through the bed of the powdered mixture of pigment and binder, the wire will pick up a considerable amount of the powder because of the high temperature of the wire and the. sticky nature of the saturant. Since the wire is at a temperature considerably above the melting point of the binder in the pigmented mixture, the particles in contact with the saturated jacket of the wire become fused together and also coalesce with the saturant and become anchored to the jacket. Any excess of loosely adhering particles of the pigmented mixture may be removed by a suitable type of wiper.

At this point the pigmented coating, although firmly anchored to the saturated jacket of the wire, may not be as dense as is desirable on the finished product. Consequently, it is preferable to pass the coated wire between one or more sets of rollers to compact the pigmented coating and force the pigmented mixture into the interstices of the fabric jacket to more securely anchor the coating.

Finally, the coated insulated wire is passed through one or more heated dies to bring the binder of the pigmented layer above its fusing point and thus completely melt the binder on and adjacent to the surface of the pigmented coating. The action of the hot' dies is to cause the melted binder to spread in a continuous film over the surface of the pigmented layer and thus to impart to the surface of the coated, insulated wire a degree of smoothness and slip that is sufilcient for most purposes.

As an additional step, but one that is not necessary and is, in any event, customary in the art, the coated insulated wire may be provided with a separately applied film of wax or wax-like substance An important feature of my invention is that the pigmented coating is continuous, dense and relatively smooth after it leaves the last heated die and has been chilled, so that the application of a final wax film is entirely optional.

While this invention has been described with particular reference to the manufacture of coated, insulated wire, it will be understood that it is applicable generally to the coating of fabric covercd strands, as in the manufacture of certain types of colored wires.

I am aware that many changes may be made and numerous details of construction may be varied through a. wide range without departing from the principles of this invention, and I,

therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

1. The method of coatinga fabric jacket of an insulated wire, which comprises impregnating said jacket with a flame repellant pitch at a temperature above the melting p0int.of said pitch, passing said wire while still hot through a powdered mixture of a pigment and binder fusible below the temperature of the hot wire, thereby forming a layer of said pigment mixture over said jacket, applying rolling pressure to said layer to compact the same and again fusing the binder in said layer to form as the final external coating a smooth, dense coherent layer of said pigment mixture firmly anchored to said jacket.

2. In the method of coating the fabric jacket of an insulated wire, the steps of saturating said fabric jacket with a liquid compound of a sticky nature, then passing said sticky saturated jacket through a powdered pigmented mixture containing a thermoplastic binder and heating the resulting coating of the pigmented mixture by itself to fuse the binder therein and form a smooth, dense coating, sufiiciently adherent and coherent to constitute the final external coating.

3. A continuous method of coating a fibrous covered strand of the class described, which com-- prises impregnating said fibrous covered strand with a pitchy saturant at an elevated temperature, while still at a temperature above the melting point of said pitchy substance passing said strand through a pulverulent mixture of pigment and thermoplastic binder to fuse said binder locally of said strand and form an adhering layer of said pigment mixture over said impregnated fibrous covering, compacting said layer and fuse ing and smoothing the surface of said layer by passage througha heated die.

ALBERT T. CANDY, JR. 

